The invention relates to a sluice system for a vacuum coating facility for coating substrates that can be moved through the vacuum coating facility in a direction of conveyance. On the input and output sides, the sluice system comprises a prevacuum sluice chamber and a transfer chamber adjoining a coating chamber, wherein a fine vacuum can be regulated before the transfer chamber on the input side in the direction of conveyance and after the transfer device on the output side in the direction of conveyance.
Sluice systems for vacuum coating facilities of this type are primarily used in industrial applications in in-line large-area coating facilities typically for flat glass substrates. The usual structure of the sluice system incorporated on both sides of the coating chamber is shown in a diagram of a through-feed sluice system for coating architectural glass in “Vakummtechnik -Grundlagen and Anwendungen”, Pupp/Hartmann, Carl Hanser Verlag, page 426. The sluice system normally consists of a prevacuum sluice chamber, a fine vacuum sluice chamber and a transfer chamber. If necessary, further fine vacuum sluice chambers with process-preparing and pressure-stabilizing functions are arranged in-line between the prevacuum sluice chamber and the transfer chamber. A prevacuum pressure of approx. 10−3 bar is generated in the prevacuum sluice chamber on the input side, in which the substrates are fed to the vacuum coating facility, and analogously in the prevacuum sluice chamber on the output side. This normally occurs via a prevacuum pump system connected to the prevacuum sluice chamber, consisting of a Roots pump, to which a rotary slide-valve pump is connected upstream as a backing pump.
The fine vacuum sluice chamber serves as a further pressure stage and pressure buffer for pressure stabilization. An intermediate vacuum with a pressure which is between the prevacuum pressure and the high-vacuum pressure, but close to that of the process vacuum pressure of the coating chambers, of approximately 10−3 bar is generated here. Normally, one or more pump systems with a power corresponding to the construction of the prevacuum pump system are connected to the fine vacuum sluice chamber. The substrates are prepared for transfer to the first coating chamber or guided out of the last coating chamber in the transfer chamber which adjoins the first and last coating chamber in the direction of conveyance respectively. A fine pressure vacuum is maintained there, which has attained the actual process vacuum pressure of approx. 10−4 bar to 10−5 bar. For this, several turbo-molecular pumps connected in parallel are normally connected to the transfer chamber to which a backing pump or a Roots pump combined with a backing pump are connected upstream. All sluice chambers of the sluice system are separated through vacuum technology among each other as well as on the atmosphere side and process side.
Increasingly high requirements are placed on the sluice system in respect to the cycles to be reduced for the total sluice time, as endeavors are increasingly being made to shorten the cycle times of vacuum coating facilities. The cycle times are determined by evacuation times, coating times and nonproductive times, that is times for transport of the substrate through the sluice chamber and the sluice valve opening and closing times. The non-productive times take up a considerable part of this and restrict a reduction of the cycle times as the evacuation times and coating times cannot be reduced further owing to physical constraints.
A reduction of the sluice cycle times typically results from the arrangement of a prevacuum sluice chamber and a transfer chamber with several pressure stages, as known from DE 198 08 163 C1. The chamber volume of the transfer chamber is divided into several buffer sections via special flow elements, with the result that a pressure decoupling of the process area from the prevacuum sluice chamber is enabled. In this way, a stabilization of the pressure gradients is achieved between the prevacuum sluice chamber and the process chamber such that the further intermediate vacuum chambers with their sluice valves are rendered superfluous. As a result, the activation times for the sluice valves no longer apply. However, the drawback to this solution is that this transfer chamber requires a high level of constructional technology and expense and occupies considerable space.